scholarly journals Response of near-surface currents in the Indian Ocean to the anomalous atmospheric condition in 2015

2018 ◽  
Vol 149 ◽  
pp. 012054
Author(s):  
P A Utari ◽  
M Y Nurkhakim ◽  
D Setiabudidaya ◽  
I Iskandar
Keyword(s):  
Indian Ocean ◽  
Atmospheric Condition ◽  
Surface Currents ◽  
Near Surface ◽  
The Indian Ocean

scholarly journals Characteristics of the Near-Surface Currents in the Indian Ocean as Deduced from Satellite-Tracked Surface Drifters. Part I: Pseudo-Eulerian Statistics

2015 ◽  
Vol 45 (2) ◽  
pp. 441-458 ◽  
Author(s):  
Shiqiu Peng ◽  
Yu-Kun Qian ◽  
Rick Lumpkin ◽  
Yan Du ◽  
Dongxiao Wang ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Kinetic Energy ◽  
Eastern Coast ◽  
Western Boundary ◽  
Surface Currents ◽  
Mean Velocity ◽  
Near Surface ◽  
The Indian Ocean ◽  
Central Eastern ◽  
Surface Drifters

AbstractUsing the 1985–2013 record of near-surface currents from satellite-tracked drifters, the pseudo-Eulerian statistics of the near-surface circulation in the Indian Ocean (IO) are analyzed. It is found that the distributions of the current velocities and mean kinetic energy (MKE) in the IO are extremely inhomogeneous in space and nonstationary in time. The most energetic regions with climatologic mean velocity over 50 cm s−1 and MKE over 500 cm2 s−2 are found off the eastern coast of Somalia (with maxima of over 100 cm s−1 and 1500 cm2 s−2) and the equatorial IO, associated with the strong, annually reversing Somalia Current and the twice-a-year eastward equatorial jets. High eddy kinetic energy (EKE) is found in regions of the equatorial IO, western boundary currents, and Agulhas Return Current, with a maximum of over 3000 cm2 s−2 off the eastern coast of Somalia. The lowest EKE (<500 cm2 s−2) occurs in the south subtropical gyre between 30° and 40°S and the central-eastern Arabian Sea. Annual and semiannual variability is a significant fraction of the total EKE off the eastern coast of Somalia and in the central-eastern equatorial IO. In general, both the MKE and EKE estimated in the present study are qualitatively in agreement with, but quantitatively larger than, estimates from previous studies. These pseudo-Eulerian MKE and EKE fields, based on the most extensive drifter dataset to date, are the most precise in situ estimates to date and can be used to validate satellite and numerical results.

scholarly journals Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

2013 ◽  
Vol 10 (10) ◽  
pp. 6677-6698 ◽  
Author(s):  
J. C. Currie ◽  
M. Lengaigne ◽  
J. Vialard ◽  
D. M. Kaplan ◽  
O. Aumont ◽  
...  
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Near Surface ◽  
Climate Modes ◽  
The Indian Ocean

Abstract. The Indian Ocean Dipole (IOD) and the El Niño/Southern Oscillation (ENSO) are independent climate modes, which frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled biophysical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997/1998 ENSO and IOD event. Results suggest that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. A negative influence of IOD on chlorophyll concentrations is shown in a region around the southern tip of India in fall. IOD also depresses depth-integrated chlorophyll in the 5–10° S thermocline ridge region, yet the signal is negligible in surface chlorophyll. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Yet unlike most other regions examined, the combined explanatory power of IOD and ENSO in predicting depth-integrated chlorophyll anomalies is relatively low in this region, suggestive that other drivers are important there. We show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. Our results suggest that ENSO and IOD cause significant and predictable regional re-organisation of chlorophyll via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries, ecosystems and carbon budgets.

Seasonal variations in the Indian Ocean along 110°E. I. Hydrological structure of the upper 500 m

1969 ◽  
Vol 20 (1) ◽  
pp. 1 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
Surface Waters ◽  
Water Masses ◽  
Surface Currents ◽  
Temperature Changes ◽  
East Indian ◽  
Hydrological Structure ◽  
The Indian Ocean ◽  
The Tropics ◽  
East Indian Ocean

Tropical and subtropical water masses at surface and subsurface depths were separated by their salinity, temperature, oxygen, and nutrient characteristics. The annual mean depths and latitudinal extent of these water masses were determined. Annual changes in the upper 50 m were generally so small relative to those found in other oceans that advection and mixing must have been less important in their genesis than local climatic changes. There was a barely significant seasonal rhythm in surface phosphate and nitrate, with peak occurrences of each some 6 months apart. At each latitude the permanent thermal discontinuity centred around a particular isotherm varied little in intensity during the year, but rose and fell in accordance with surface currents. The thermocline south of c. 18�S. varied little in depth but greatly in intensity during the summer. The depth of the mixed layer was much less in summer and at all times shallower in the tropics. The depth of this layer was governed more by the accumulation of surface waters by zonal currents and eddies, than by wind stress or convective overturn. Therefore there was little difference from south to north, or month to month, in average nutrient values of this mixed column. The movement of the various surface waters, deduced from salinity and temperature changes during the year, usually agrees with geostrophic currents across 110�E, and ships' observations of surface currents in the south-east Indian Ocean.

scholarly journals On the Indonesian throughflow in the OCCAM 1/4 degree ocean model

2007 ◽  
Vol 4 (2) ◽  
pp. 325-370 ◽  
Author(s):  
U. W. Humphries ◽  
D. J. Webb
Keyword(s):  
Indian Ocean ◽  
Ocean Model ◽  
Global Ocean ◽  
Indonesian Throughflow ◽  
Island Rule ◽  
Near Surface ◽  
The North ◽  
The Pacific ◽  
The Indian Ocean ◽  
Pass Through

Abstract. The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degree global ocean model, one using monthly climatological winds and one using ECMWF analysed six-hourly winds for the period 1993 to 1998. The long-term model throughflow agrees with observations and the value predicted by Godfrey's Island Rule. The Island Rule has some skill in predicting the annual signal each year but is poor at predicting year to year and shorter term variations in the total flow especially in El Nino years. The spectra of transports in individual passages show significant differences between those connecting the region to the Pacific Ocean and those connecting with the Indian Ocean. This implies that different sets of waves are involved in the two regions. Vertical profiles of transport are in reasonable agreement with observations but the model overestimates the near surface transport through the Lombok Strait and the dense overflow from the Pacific through the Lifamatola Strait into the deep Banda Sea. In both cases the crude representation of the passages by the model appears responsible. In the north the model shows, as expected, that the largest transport is via the Makassar Strait. However this is less than expected and instead there is significant flow via the Halmahera Sea. If Godfrey's Island Rule is correct and the throughflow is forced by the northward flow between Australia and South America, then the Halmahers Sea route should be important. It is the most southerly route around New Guinea to the Indian Ocean and there is no apparent reason why the flow should go further north in order to pass through the Makassar Strait. The model result thus raises the question of why in reality the Makassar Strait route appears to dominate the throughflow.

scholarly journals Atmospheric pollutant outflow from southern Asia: a review

2010 ◽  
Vol 10 (22) ◽  
pp. 11017-11096 ◽  
Author(s):  
M. G. Lawrence ◽  
J. Lelieveld
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Scale Effects ◽  
Long Distance ◽  
Atmospheric Pollutant ◽  
Near Surface ◽  
Air Masses ◽  
Southern Asia ◽  
The Indian Ocean

Abstract. Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea, is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the summer monsoon, and the monsoon transition periods. During winter, the near-surface flow is mostly northeasterly, and the regional pollution forms a thick haze layer in the lower troposphere which spreads out over millions of square km between southern Asia and the Intertropical Convergence Zone (ITCZ), located several degrees south of the equator over the Indian Ocean during this period. During summer, the heavy monsoon rains effectively remove soluble gases and aerosols. Less soluble species, on the other hand, are lifted to the upper troposphere in deep convective clouds, and are then transported away from the region by strong upper tropospheric winds, particularly towards northern Africa and the Mediterranean in the tropical easterly jet. Part of the pollution can reach the tropical tropopause layer, the gateway to the stratosphere. During the monsoon transition periods, the flow across the Indian Ocean is primarily zonal, and strong pollution plumes originating from both southeastern Asia and from Africa spread across the central Indian Ocean. This paper provides a review of the current state of knowledge based on the many observational and modeling studies over the last decades that have examined the southern Asian atmospheric pollutant outflow and its large scale effects. An outlook is provided as a guideline for future research, pointing out particularly critical issues such as: resolving discrepancies between top down and bottom up emissions estimates; assessing the processing and aging of the pollutant outflow; developing a better understanding of the observed elevated pollutant layers and their relationship to local sea breeze and large scale monsoon circulations; and determining the impacts of the pollutant outflow on the Asian monsoon meteorology and the regional hydrological cycle, in particular the mountain cryospheric reservoirs and the fresh water supply, which in turn directly impact the lives of over a billion inhabitants of southern Asia.

scholarly journals On the Indonesian Throughflow in the OCCAM 1/4 degree ocean model

Ocean Science ◽  
2008 ◽  
Vol 4 (3) ◽  
pp. 183-198 ◽  
Author(s):  
U. W. Humphries ◽  
D. J. Webb
Keyword(s):  
Indian Ocean ◽  
Ocean Model ◽  
Global Ocean ◽  
Indonesian Throughflow ◽  
Island Rule ◽  
Near Surface ◽  
The North ◽  
The Pacific ◽  
The Indian Ocean ◽  
Pass Through

Abstract. The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degree global ocean model, one using monthly climatological winds and one using ECMWF analysed six-hourly winds for the period 1993 to 1998. The long-term model throughflow agrees with observations and the value predicted by Godfrey's Island Rule. The Island Rule has some skill in predicting the annual signal each year but is poor at predicting year to year and shorter term variations in the total flow, especially in El Niño years. The spectra of transports in individual passages show significant differences between those connecting the region to the Pacific Ocean and those connecting with the Indian Ocean. On investigation we found that changes in the northern transports were strongly correlated with changes in the position of currents in the Celebes Sea and off Halmahera. Vertical profiles of transport are in reasonable agreement with observations but the model overestimates the near surface transport through the Lombok Strait and the dense overflow from the Pacific through the Lifamatola Strait into the deep Banda Sea. In both cases the crude representation of the passages by the model appears responsible. In the north the model shows, as expected, that the largest transport is via the Makassar Strait. However this is less than expected and instead there is significant flow via the Halmahera Sea. If Godfrey's Island Rule is correct and the throughflow is forced by the northward flow between Australia and South America, then the Halmahers Sea route should be important. It is the most southerly route around New Guinea to the Indian Ocean and there is no apparent reason why the flow should go further north in order to pass through the Makassar Strait. The model result thus raises the question of why in reality the Makassar Strait route appears to dominate the throughflow.

Surface Currents of the Ocean and their effects on Navigation

1954 ◽  
Vol 7 (4) ◽  
pp. 343-361
Author(s):  
C. E. N. Frankcom ◽  
E. W. Barlow
Keyword(s):  
Indian Ocean ◽  
Gulf Stream ◽  
West Indies ◽  
Ocean Currents ◽  
Surface Currents ◽  
The South ◽  
The West ◽  
The Indian Ocean

One of the earliest publications about ocean currents was Dampier's Discourse of Winds, Breezes, Storm Tides and Currents published in about 1700. Dampier wrote his book in 1688 and he says:By currents I mean a motion of the sea which is different from the tides in several respects—both as to its duration and also as to its course; currents run a day, a week, nay sometimes more one way, then it may be, run another way. In some places they run six months one way and six months another. In some places they run constantly one way and never shift at all.After some remarkably detailed discussion of currents in the West Indies and off the coast of Africa and in the south seas he says, of the Indian Ocean currents, ‘north of the line the current stays with the monsoon but does not shift altogether so soon, sometimes not for three weeks or more and then never shifts again till the monsoon is settled in the contrary way’. Of the Gulf Stream he says, ‘near the shores on each side of this Gulf there are tides, especially on the Florida shore, and ships may pass which way they please, if they are acquainted’. In conclusion he says, ‘I humbly offer this not as a complete and perfect account but as a rude and imperfect beginning or specimen of what may be done by abler hands hereafter’.

Sign in / Sign up

Export Citation Format

Share Document